CN113094927B - Method for realizing multi-channel information coding by using novel optical film - Google Patents

Abstract

The invention discloses a method for realizing multi-channel information coding by using a novel optical film, which comprises the following steps: 1) Constructing a nanostructure unit; 2) Optimizing the structural parameters of the nanostructure elements according to the wavelength lambda of incident light; 3) Constructing a nanostructure array comprising a plurality of nanostructure elements; set to the polarization direction alpha ₁ Linearly polarized light of which the value is not less than pi/2 is incident to the nano structure array and then passes through the alpha direction of the light transmission axis ₂ A polarization analyzer of =0 capable of encoding a first image on the nanostructure array; linearly polarized light with the polarization direction unchanged is incident to the nanostructure array and then is transmitted to alpha from the light transmission axis direction ₂ A polarization analyzer of = pi/4, capable of encoding a second image on the surface of the nanostructure array; off-normal direction alpha ₁ Linearly polarized light of which the frequency is not less than-pi/8 is incident to the nanostructure array and then passes through the direction alpha of a light transmission axis ₂ The analyzer with the color value of = pi/8 can encode a third image on the surface of the nanostructure array, and can be applied to the fields of polarization display, encryption, high-end anti-counterfeiting and the like.

Description

A method for multi-channel information encoding using a novel optical film

technical field

The invention belongs to the technical fields of micro-nano optics and polarization optics, and in particular relates to a method for realizing multi-channel information coding by using a novel optical film.

Background technique

Metasurface material is a new type of nanomaterial composed of arrays of subwavelength structures and capable of super-tuning light waves. Its appearance provides a new method for realizing the miniaturization, integration and high performance of optoelectronic devices. With the continuous development of information technology, how to realize the storage and encoding of large-capacity information is a problem that is widely concerned in the field of optoelectronics.

In order to increase the information capacity of the device and improve the functionality of the device, many multi-channel information encoding methods based on metasurface materials have been proposed one after another. According to the type of nanostructure, they can be roughly divided into three categories: 1) Multi-channel information encoding methods based on variable-angle nanostructures Channel information coding method; 2) Multi-channel information coding method based on variable size nanostructure; 3) Multi-channel information coding method based on variable rotation angle and variable size nanostructure.

At present, the encoding methods based on variable-size nanostructures or variable-size-plus-angle nanostructures have relatively high processing requirements, while encoding methods based on variable-angle nanostructures often sacrifice image quality in exchange for the number of encoding channels. Essentially, Information capacity has not been improved. In this paper, a three-channel information encoding method is proposed based on variable-angle nanostructures.

Contents of the invention

In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for realizing multi-channel information encoding by using a new type of optical film. By ingeniously designing the steering angle of the nanostructure in the new type of optical film, the information between the three channels can be realized. Conversion, has a good development prospect in the fields of high-end anti-counterfeiting, polarization display, image hiding and so on.

The invention provides a method for realizing multi-channel information encoding by using a novel optical film, which includes the following steps:

1) Build a nanostructure unit; the nanostructure unit includes a transparent base and a nano-brick deposited on the base working surface, and the xoy coordinate system is established with the right-angled side of the structural unit as the x-axis and the y-axis, and the long side of the nano-brick is the length The axis and the short side are short axes, and the angle between the long axis of the nano-brick and the x-axis is the steering angle θ of the nano-brick;

2) optimize the structural parameters of the nanostructure unit according to the incident light wavelength λ, the structural parameters include: the side length C of the base working surface and the long axis L, short axis W, and height H of the nano bricks;

3) Construct a nanostructure array, the nanostructure array includes a plurality of nanostructure units; set the linearly polarized light with the polarization direction α ₁ = π/2 to enter the nanostructure array and then pass through the light transmission axis direction α ₂ = 0, the first image can be encoded in the nanostructure array; the linearly polarized light whose polarization direction remains unchanged enters the nanostructure array and then passes through the detector in the direction of the transmission axis to α ₂ =π/4 A polarizer, capable of encoding the second image on the surface of the nanostructure array; the linearly polarized light in the polarization direction α ₁ =-π/8 is incident on the nanostructure array and then passes through the light transmission axis direction α ₂ =π/8 The analyzer can encode the third image on the surface of the nanostructure array, that is, on an array composed of nanostructures with variable rotation angles, the simultaneous encoding of three images can be realized.

Further, the transparent substrate in step 1) is fused silica glass material, and the nano bricks are gold, silver, aluminum or silicon material.

Further, the structural parameters of the nanostructure unit in the step 2) are obtained through electromagnetic simulation optimization according to the selected wavelength λ of the incident light.

Further, in step 3), each nanostructure unit in the nanostructure array is equivalent to a polarizer. When the linearly polarized light passes through the nanobrick polarizer and then the analyzer, the outgoing light intensity can be expressed as:

In the formula: I ₀ is the intensity of the incident polarized light, θ is the steering angle of the nano-brick, α ₁ is the polarization direction of the incident ray polarized light, and α ₂ is the transmission axis direction of the analyzer;

a. The polarization direction of the incident ray polarized light is perpendicular to the transmission axis of the analyzer (α ₂ =α ₁ +π/2), and the output light intensity can be simplified as:

Among them, by adjusting the steering angle θ of the nano-bricks, the continuous adjustment of the outgoing intensity can be realized; when the polarization direction of the incident light is α1=π/2, α2=0, the outgoing light intensity is

b. When the polarization direction of the incident ray polarization is α ₁ = π/2, and the direction of the transmission axis of the analyzer is α ₂ = π/4, the outgoing light intensity can be simplified as

c. When the polarization direction of the incident ray polarization is α ₁ =-π/8, and the direction of the transmission axis of the analyzer is α ₂ =π/8, the outgoing light intensity can be simplified as

Further, the intensity variation relationship of the three kinds of outgoing light intensity modulation functions in the value range [0, π] of the steering angle θ of the nano-bricks is:

a. When the steering angle θ of the nano-brick changes in the range of [0, π/8], its corresponding intensity I ₁ can realize continuous modulation of 0-0.5, the intensity of I ₂ is less than 0.5, and the intensity of I ₃ is greater than 0.5;

b. When the steering angle θ of nanobricks changes within the range of [3π/8,π/2], the corresponding intensity I ₁ can also achieve continuous modulation from 0-0.5, the intensity of I ₂ is greater than 0.5, and the intensity of I ₃ less than 0.5;

c. When the steering angle θ of nanobricks changes in the range of [π/2,5π/8], its corresponding intensity can still achieve continuous modulation of 0-0.5, the intensity of I ₂ is greater than 0.5, and the intensity of I ₃ is greater than 0.5 ;

d. When the steering angle θ of the nano-brick changes in the range of [7π/8,π], its corresponding intensity can still achieve continuous modulation of 0-0.5, the intensity of I ₂ is less than 0.5, and the intensity of I ₃ is less than 0.5;

By rationally arranging the steering angles of nanobricks, three images can be encoded simultaneously on one metasurface.

Furthermore, the new film is nano-bricks with different corners and the same size, in which the nano-bricks are micro-nano polarizers, which can reflect or transmit linearly polarized light incident along the long axis of the nano-bricks, and at the same time transmit or reflect light along the short axis of the nano-bricks. Incident linearly polarized light.

Further, the first image is a continuous grayscale image, and both the second image and the third image are binary images.

Compared with prior art, the beneficial effect of the present invention:

1) By adopting the technical solution of the present invention, the three images formed by the variable-angle nanostructure array under different polarization states can be designed separately, wherein the images of channel 1 and channel 2 have no correlation and cannot be inferred from each other, and can be designed arbitrarily. The image of 3 is not related to the image of channel 1, but is related to the image of channel 2, but the conversion between the three channels can be realized by rotating the polarizer and analyzer, so it can be used in polarization display, encryption, high-end anti-counterfeiting and other fields , to provide a new method and approach for future security technology;

2) The design method of the present invention proposes a new degree of freedom of light wave manipulation, the design method is ingenious, the processing difficulty is low, the structure used is simple, and only one nano-brick structural unit is needed to realize the encoding of three nano-printed images, so The metasurface designed by the present invention is small in size, light in weight, highly integrated, and suitable for the development of miniaturization and miniaturization in the future;

3) The first channel image produced by the present invention is a continuous grayscale image, the second channel and the third channel are binary images, the pattern can be generated arbitrarily, the decoding conditions are different, and it is not easy to be imitated and forged, so users can apply For high-end watches, luxury goods, chips and other devices that require anti-counterfeiting;

4) The novel optical film of the present invention can work both in the transmission mode and in the reflection mode.

Description of drawings

Fig. 1 is the schematic diagram of nano-brick structural unit in the present embodiment;

Fig. 2 is the scanning diagram of the transmittance and reflectance of the nanostructure unit in the present embodiment;

Fig. 3 is a schematic diagram of the relationship between the intensity modulation function and the steering angle of nano bricks in the present embodiment;

Fig. 4 is the continuous grayscale nanoprinting image of the first channel designed in the present embodiment;

Fig. 5 is the binary image of the second channel designed in the present embodiment;

Fig. 6 is a binary image of the third channel designed in this embodiment.

Detailed ways

The present invention will be further described below in conjunction with the examples, but the protection scope of the present invention is not limited to the said scope.

Example 1

A method for realizing multi-channel information encoding by using a novel optical film, the specific steps are as follows:

First, construct the nano-structure unit, as shown in Figure 1, the nano-unit structure is composed of silver nano-bricks and a silicon base layer, and secondly, select the design wavelength as λ=633nm, for this wavelength, use the electromagnetic simulation software CST to convert the nano-structure unit The optimization simulation is carried out, and the size parameters of the optimized silicon nano-bricks are: the length is L=130nm, the width is W=85nm, the height is H=70nm, and the side length of the unit structure base is C=400nm.

_The transmission and reflection efficiency of nanobricks for linearly polarized light incident along the long and short axes of nanobricks under this structural parameter is shown in Fig _. Light efficiency, where T _l and T _s represent the transmitted light efficiency along the long axis and short axis of the nanobrick, respectively.

It can be seen from Figure 2 that at the working wavelength of 633nm, R _l is as high as 80%, R _s is suppressed below 1%, T _s is above 90%, and T _l is suppressed below 1%, indicating that the incident along the long axis of the nanobrick The light is completely reflected, and the light incident along the short axis of the nano-brick is almost completely transmitted. Therefore, the optimized nano-brick unit structure can realize the function of polarization splitting, that is, a transmissive polarizer and a reflective polarizer. .

Finally, a nanostructure array is constructed. The nanostructure array contains a plurality of nanostructure units. When the linearly polarized incident light passes through the nanostructure array and then the analyzer, the light transmission axis of the polarizer and the analyzer is changed. direction, different light intensity modulation functions can be obtained, and the transformation relationship between it and the azimuth angle of the nano-brick is shown in Figure 3. When the azimuth angle of the nano-brick changes in the range of [0, π/8] (area #1) , the corresponding intensity I ₁ can realize the continuous modulation of 0-0.5, the intensity of I ₂ is less than 0.5, and the intensity of I ₃ is greater than 0.5; when the azimuth angle of the nano brick changes in the range of [3π/8, π/2] ( In region #2), its corresponding intensity I ₁ can also achieve continuous modulation of 0-0.5, I ₂ is greater than 0.5, and the intensity of I ₃ is less than 0.5. When the azimuth angle of the nanobrick varies in the range of [π/2,5π/8] (region #3), its corresponding intensity can still achieve continuous modulation from 0 to 0.5, I ₂ is greater than 0.5, and the intensity of I ₃ is greater than 0.5. When the azimuth angle of nanobricks varies in the range of [7π/8, π] (region #4), its corresponding intensity can still achieve continuous modulation from 0-0.5, and the intensity of I ₂ is less than 0.5, and the intensity of I ₃ is less than 0.5. Therefore, based on this principle, three images can be designed and generated on a structured surface at the same time, a continuous grayscale image as shown in Figure 4, and two binary images as shown in Figures 5 and 6.

Claims (3)

1. A method utilizing novel optical film to realize multi-channel information encoding, characterized in that it comprises the steps: 1) Build a nano-structure unit; the nano-structure unit includes a transparent substrate and a nano-brick deposited on the base working surface, and the x-axis and the y-axis set up a xoy coordinate system with the right-angled side of the structural unit, and the long side of the nano-brick is long Axes and short sides are short axes, and the angle between the long axis and the x-axis of the nano-bricks is the steering angle θ of the nano-bricks; 1) the transparent substrate described in the step is a fused silica glass material, and the nano-bricks are gold , silver, aluminum or silicon materials; 2) Optimizing the structural parameters of the nanostructure unit according to the incident light wavelength λ, the structural parameters include: the side length C of the base working surface and the long axis L, short axis W, and height H of the nano bricks; 3) Construct a nanostructure array, the nanostructure array includes a plurality of nanostructure units; set the linearly polarized light with the polarization direction α ₁ = π/2 to enter the nanostructure array and then pass through the light transmission axis direction α ₂ = 0, the first image can be encoded in the nanostructure array; the linearly polarized light whose polarization direction remains unchanged enters the nanostructure array and then passes through the detector in the direction of the transmission axis to α ₂ =π/4 The polarizer can encode the second image on the surface of the nanostructure array; the linearly polarized light with the polarization direction α ₁ =-π/8 is incident on the nanostructure array and passes through the detector with the transmission axis direction α ₂ =π/8 The polarizer can encode the third image on the surface of the nanostructure array, that is, on an array composed of nanostructures with variable rotation angles, the simultaneous encoding of three images can be realized; 3) In the step, each nanostructure unit in the nanostructure array is equivalent to a polarizer. When the linearly polarized light passes through the nanobrick polarizer and then the analyzer, the emitted light intensity can be expressed as:

In the formula: I ₀ is the intensity of the incident polarized light, θ is the nanobrick steering angle, α ₁ is the polarization direction of the incident ray polarized light, and α ₂ is the transmission axis direction of the analyzer; a. The polarization direction of the incident linearly polarized light is perpendicular to the transmission axis of the analyzer α ₂ =α ₁ +π/2, and the output light intensity can be simplified as:

The output intensity can be continuously adjusted by adjusting the steering angle θ of the nano-bricks; when the incident light polarization direction α ₁ =π/2, α ₂ =0, the output light intensity is

b. When the polarization direction of the incident ray polarized light is α ₁ = π/2, and the direction of the transmission axis of the analyzer is α ₂ = π/4, the outgoing light intensity can be simplified as

c. When the polarization direction of the incident ray polarized light is α ₁ =-π/8, and the transmission axis direction of the analyzer is α ₂ =π/8, the exit light intensity can be simplified as

The intensity variation relationship of the three outgoing light intensity modulation functions in the range [0, π] of the steering angle θ of the nano-bricks is: a. When the steering angle θ of the nano-brick changes in the range of [0, π/8], its corresponding intensity I ₁ can realize continuous modulation of 0-0.5, the intensity of I ₂ is less than 0.5, and the intensity of I ₃ is greater than 0.5; b. When the steering angle θ of nanobricks changes within the range of [3π/8,π/2], the corresponding intensity I ₁ can also achieve continuous modulation from 0-0.5, the intensity of I ₂ is greater than 0.5, and the intensity of I ₃ less than 0.5; c. When the steering angle θ of the nano brick changes in the range of [π/2,5π/8], its corresponding intensity I ₁ can still achieve continuous modulation of 0-0.5, the intensity of I ₂ is greater than 0.5, and the intensity of I ₃ Greater than 0.5; d. When the steering angle θ of nanobricks changes within the range of [7π/8,π], the corresponding intensity I ₁ can still achieve continuous modulation from 0-0.5, the intensity of I ₂ is less than 0.5, and the intensity of I ₃ is less than 0.5 ; By rationally arranging the steering angle of nano-bricks, three images can be encoded simultaneously on one metasurface; The new optical film is nano-bricks with different rotation angles and the same size. The nano-bricks are micro-nano polarizers, which can reflect or transmit linearly polarized light incident along the long axis of the nano-brick, and at the same time transmit or reflect the incident light along the short axis of the nano-brick. of linearly polarized light. 2. A method for utilizing novel optical thin films to realize multi-channel information encoding according to claim 1, characterized in that 2) the structural parameters of the nanostructure unit in the step are based on the selected incident light wavelength λ, by electromagnetic The simulation optimization is obtained. 3. A method of utilizing novel optical films to realize multi-channel information encoding according to claim 1, characterized in that the first image is a continuous grayscale image, and the second image and the third image are binary images .

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